Research On High Precision Current Sensors And Related Algorithms

Current sensors are widely used in various areas including power electronics,automobile,consumer electronics.With the rapid development of electronic systems,the resolution and stability of current detection are required to be higher and higher.Therefore,the performances of the current sensor need to be improved to meet the requirements of different applications.However,the noise in the circuit makes it hard to improve the resolution of current sensor.Solving the noise problem is the key to improve the measuring precision.In this thesis,a design scheme of high precision current detection is presented,which is based on modulation-demodulation technology and digital average algorithm to suppress circuit noise and improve current detection accuracy.The designed modulation and demodulation circuit can modulate the low-frequency signal to the high-frequency band,and then demodulate and filter the lowfrequeney noise in the sensor.The digital average algorithm is used to reduces and eliminates the influence of random noise and suppresses the Gaussian white noise in the circuit.The principle of modulation-demodulation circuit and digital average algorithm for noise suppression are described in detail.MATLAB is used to build simulation model,and the feasibility of the system design is verified.The system design of current sensor is realized from two aspects of hardware and software.The hardware includes the schemes comparison,chip selection and circuit design.The software includes the design of microprocessor initialization,peripheral driver and average algorithm.In addition,the GUI user interface of the upper computer is provided by using MATLAB,which is used to communicate with the signal processing circuit of current sensor,display data and print waveform.Finally,the stability and reliability of the current sensor circuit are verified by testing,and the effect of digital average algorithm used in circuit filtering is also verified by measurement results.The sensitivity of the current sensor is 0.618 V/A,and the linearity is about 1.3%.The measured AC magnetic field amplitude range is 0-18 Gs,the measurable AC current amplitude range is 0-900mA,and the measurement accuracy is 0.16%.The application of digital average algorithm has the function of smoothing the signal waveform.The output signal-to-noise ratio is increased by about 7 times after 50 times of digital average processing,which effectively suppresses the circuit noise and improves the signal-to-noise ratio of the output signal.The circuit of current sensor system shows high stability and strong anti-interference ability,and the main functions and performance indexes meet the design requirements.